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Old 07-26-2008, 12:17 PM   #16
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Listed for grounding or not


Chris and Stub-

I had to hop off the 'puter last night. Wife doesn't appreciate me being on it all night after being at work all day...

First of all, you guys are both great electricians and I hope you didn't take what I said in the wrong way. Nothing but good conversations and karma here!

Chris, I know that the idea of emt w/o egc's is a big deal to a lot of people and the subject of quite a lot of debate. What is the most important aspect of a ground? I think we'd all agree that it is establishing the lowest impedance path between the device and source. That being said, the biggest issue with using a raceway system as the egc lies within how it is constructed. Certainly, if you do not tighten the locknuts, comp. fittings and set screws, you are adversely affecting the bonding performance of the system. And these items are listed for a purpose. Why would the CMP accept them for grounding if they were not (and this will most certainly lead to a lot of hootin' and hollerin' before this is over!)?

I seem to remember a post not too long ago where the OP found an instance where all of the ground conductors in a box were simply left unterminated/loose. Obviously, the efficacy of this grounding method is zero. So in the end, the final product and its ability to perform all the functions for which it is intended lies in the diligence, knowledge and professionalism of the installer.

As a DIYer, I actually pay a lot of attention to the types of fittings and whatnot that I use. Earlier on, I used to seek out the T&B steel box connectors since the locknut teeth were somewhat concave like a belleville washer. When you tightened them down, they were bent against the box surface which put them into compression therein decreasing the likelihood that they would loosen over time. Also, their exterior bodies are shaped like a nut making it easy to grab the lockut and twist the body with channels or a wrench. Now I've fallen for the Appleton 2-pc. connectors. They are a bit more expensive but they allow me to install my boxes first and then pipe between them. Also, it is very easy, compared to a locknut, to put a crescent or 1" open-end wrench on a nut which is on the exterior of the box for the purposes of making that thing good and tight.

After doing all of the pipe and wire for my new boiler and HVAC equipment, I went to power up the 120 circuit for the boiler controls. Seems that when I tightened down one of the blister cover screws for the local disconnect, the screw threads dug right into the wiring in the box. That breaker handle tripped back immediately as I flipped it on. So, this system, where my egc was the raceway system, obviously provided a pretty low-impedance ground path.

Anyway, that is where I stand on the issue. Fire away-I know it's coming!

Take care,
Jimmy

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Old 07-26-2008, 12:28 PM   #17
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Does anybody know if it is required to do so in the Chicago area where metal conduit is common in residences?
Stub-

All excellent points herein. I finally posted my follow up before reading this.

To answer your question, no, an explicit egc is NOT required to be run through the raceways in residential work here in Chicago. Like you say though, I always see this done in commercial/industrial.

JV-Don't want to let you down, but no, I do not do it except for special situations. I take a lot of care in installing my raceway systems and making sure that everything is tight and I feel that this provides an ample return path (I've had a few experiences to prove it).

I converted a room into a home theater/family room. I put in a special in-wall surge protector device just for my plasma. In this instance, I did in fact run a dedicated egc all the way back to the panel. Also, when I use greenfield, I always run an egc, irrespective of it's length. I've tried to find studies that would reveal what type of impedance per length this stuff presents to fault current and to date, I've come up dry (if anyone has seen something, pls. let me know). Until I can find the facts and convince myself that what I'm doing is overkill, I'll simply continue putting the egc's in there.

All good conversations,
Jimmy
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Old 07-26-2008, 12:55 PM   #18
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Listed for grounding or not


Quote:
First of all, you guys are both great electricians and I hope you didn't take what I said in the wrong way. Nothing but good conversations and karma here
!

Heck no.... never looked at it that way. This has just been a conversation and discussion that has revealed some good information among professionals.
And with respect I might add. I've spent a lot of time on many forums and have on more than one occassion got my hair up to some replies. I have come to realize that is not very productive and it is better to just make your case as best you can without being insulting.


It's when we all agree on something that would worry me..... If one wants to one up the NEC and add a little assurance to providing an effective fault path... I would find it hard to find error in that mind set.
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Old 07-26-2008, 01:06 PM   #19
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If one wants to one up the NEC and add a little assurance to providing an effective fault path... I would find it hard to find error in that mind set.
You know, I spent some time looking at the credentials for some of the people on the CMP. While pretty respectable, I don't always agree with the intent of some of the articles. I spend more time trying to understand what prompted some of the things in the code. They seem to go to extremes over some articles and kind of take a 1/2-a** view of others. I think that it would be fun to be a participant. I wonder how many ridiculous recommendations they get!

Jimmy
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Old 07-26-2008, 02:58 PM   #20
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Listed for grounding or not


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For sometime I have been unable to document which metal box covers are listed for grounding. Any of you guys know what the latest is...?

I'm told there is something in the new 2008 about this . I am being informed that the flat cornered covers ( see images below) are listed for grounding and the round ones are not. Being retired but having installed many of these covers we were never red tagged for not grounding the metal yolks of devices as long as they were attached to the covers with at least 2 screws.

Stubbie.,

The flat corner device cover on the left photo is the most common one I used and Yes they can be used with self grounding devices, Mais { But} my SOP is run the ground wire from the device to the ground screw or grounded conductor{s}.

The rounded corner on right photo I do use that once a while but not really widespread and it automatically have to run grounded pigtail due the cover will not always sit squared on the box itself. { sometime it will be partally on properly }

Merci,Marc
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Old 07-26-2008, 04:54 PM   #21
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Listed for grounding or not


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Chris and Stub-



First of all, you guys are both great electricians and I hope you didn't take what I said in the wrong way. Nothing but good conversations and karma here!


Jimmy
I was just being a pot stirrer... . I have my own opinions on how I wire things and what codes I take advantage of, but its up to the installer, and thats just the way I just feel, but as long as it meets code its a good install to me.

Last edited by chris75; 07-27-2008 at 01:51 PM.
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Old 07-27-2008, 07:29 AM   #22
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Thanks Chris

That is exactly what I'm looking for,...yeah you would think the UL white book would have it but I can't find it.

For anyone who doesn't have a copy - 2007 UL White Book.
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Old 07-27-2008, 10:14 AM   #23
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Listed for grounding or not


I agree with you regarding commercial installations. I guess I go a little over board when it comes to grounding. My house is wired in NM, but my basement is all EMT. I pulled EGC's in all the runs down there. With the cost of wire these days, I can see where even I, might forgo the almighty EGC.
I do know that the city code here requires it in commercial. I am not sure what the rule is with residential.

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